Enantioselective catalytic ?-amination through proton-coupled electron transfer followed by stereocontrolled radical-radical coupling.

ABSTRACT: A new mechanistic approach for the catalytic, enantioselective conjugate addition of nitrogen-based nucleophiles to acceptor-substituted alkenes is reported, which is based on a visible light induced and phosphate base promoted transfer of a single electron from a nitrogen nucleophile to a catalyst-bound acceptor-substituted alkene, followed by a stereocontrolled C-N bond formation through stereocontrolled radical-radical coupling. Specifically, N-aryl carbamates are added to the ?-position of ?,?-unsaturated 2-acyl imidazoles using a visible light activated photoredox mediator in combination with a chiral-at-rhodium Lewis acid catalyst and a weak phosphate base, affording new C-N bonds in a highly enantioselective fashion with enantioselectivities reaching up to 99% ee and >99?:?1 dr for a menthol-derived carbamate. As an application, the straightforward synthesis of a chiral ?-amino acid ester derivative is demonstrated.

SUBMITTER: Zhou Z 

PROVIDER: S-EPMC5621506 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature